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Typical mistakes when joint-sealing nora® rubber floor
coverings and how to avoid them
nora® rubber floor coverings do not contain any plasticizers as do e.g. PVC floor
coverings. These may thus not drift and result in shrinking floor coverings. nora®
rubber floor coverings are thus extremely dimensionally stable when bonded and
meet the standard EN 434 “Determination of dimensional stability after exposure to
heat" without any problems.
Because of these specific properties, the subsequent joint-sealing of tiles and rolls
is not necessary. Compared to other resilient floor covering materials, such as e.g.
PVC and linoleum, several advantages result from this: An attractive visual
impression is created thanks to the uniform surface, without any irritating seams.
There are no easily soiling joints. Cost benefits result from the savings in time,
wages and material.
Figure 1: Surface without joint-sealing
Usual cleaning methods such as e.g. by single-disc machines, cleaning machines
or wet mopping can, of course, also be used with complete confidence for surfaces
without joint-sealing.
Joint-sealing is solely required in a few special application areas. Because of
hygiene requirements, as e.g. those existing in hospitals, the hygiene officers often
request a joint-sealing. We also recommend joint-sealing in areas where water
remains on the floor for a longer period of time (nautical cleaning). Our acoustic
floor coverings are a further exception. Seams must be closed here because of
their high resilience. The same applies to our ed floor coverings.
If a joint-sealing is made for the above mentioned reasons or if this is requested
project-specifically, various mistakes may occur when using nora® hot-welding rod
or joint sealing compound.
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This article is to exemplify typical mistakes when joint-sealing nora® rubber floor
coverings and to show how to avoid them.
A. Joint-sealing with hot-welding rod:
In practice, joint connections using hot-welding rod is the method most commonly
used for all resilient floor coverings - this is also true for rubber floor coverings.
Joint-sealing should be made 24 hours after bonding of the floor covering at the
earliest.
What has to be observed or which mistakes can be made in this respect?
1. Premature evaluation of the adhesion of the hot-welding rod:
From time to time we receive phone calls complaining about lacking adhesion of
the hot-welding rod. Contrary to PVC, linoleum and rubber floor coverings are
thermobonded with the hot-welding rod which can be removed from the milled joint
after fitting and immediate racking.
Figure 2: Hot-welding rod removed when still hot
The protruding part may thus only be cut off after cooling down in two work steps
with a Saddler’s knife ground to a sharp edge using a weld spatula guide.
2. Wrong temperature and speed:
The right processing temperature, which ranges between 350 – 400°C, has an
important influence on the adhesion and proper processing.
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Figure 3: The correct processing temperature ranges between 350 - 400°C
The hot-welding rod is fitted using either the hand-operated hot welding gun or a
welding machine. The correct operating temperature is reached when the hotwelding rod wells out slightly on the left-hand and right-hand edges of the joint. It is
also to be noted that the welding speed is lower compared with linoleum or PVC
floor coverings.
If the processing temperature is too high, discolourations inevitably occur as shown
by the following image:
Figure 4: Discolourations caused by excessive processing temperature
For detailed work instructions, please visit our installation recommendations on our
Website www.nora.com
3. Damages caused by non-sharp trimming knife
Unfortunately, blunt trimming knives are frequently used to cut the protruding part.
The following images show a Saddler’s knife how it should not look and the
resulting scratches:
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Figure 5: Blunt trimming knife … .
Figure 6: … and the resulting scratches
The aforesaid damages to the floor covering surface may normally be well-hidden
by using a wax-containing care product. nora® liquid wax has also proven itself as
quick solution for such cases. Any occurring differing brilliance levels are
correspondingly compensated for during the routine cleanings.
4. Removal of protrusions
As the following figure shows, slight protrusions of the hot-welding rod cannot be
removed entirely by cutting. The floor covering surface is inevitably damaged.
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Figure 7: Damages when removing protruding hot-welding rod
In such cases, melting off of the protruding part using a non-sharpened spatula
which is heated up by means of the hand-operated hot welding gun and run along
the joint has proven itself as suitable method. The protruding part of the hotwelding rod can thus be easily levelled.
5. Joint-sealing of noraplan® acoustic floor coverings
The joint-sealing of noraplan® acoustic floor coverings may present a certain
challenge to untrained persons. This is because the hot-welding rod only protrudes
insufficiently because of the resilience of the material to make a clean second cut.
We thus recommend fixing two or three layers of self-adhesive copper tape under
the weld spatula guide so that there remains sufficient material after the first cut for
a clean second cut.
Figure 8: Weld spatula guide with affixed self-adhesive copper tape
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Figure 9: Sufficient protrusion for a second clean cut
B. Joint-sealing with nora® joint sealing compound:
If a norament® floor covering must be joint-sealed, the use of nora® joint-sealing
compound has proven itself already for many years. The joint-sealing compound
must also be used to close the seams between the floor covering level and a wall
covering. The same applies in this connection to external and internal corners and
joint-sealings of floor coverings at skirtings with a broad base.
1. Waxing of the floor covering joints to be joint-sealed
The seam area is to be sufficiently waxed with nora® liquid wax to be able to
subsequently remove the protrusions easily from the floor covering surface.
Otherwise, the joint-sealing compound may adhere to the surface and can only be
removed using greatest efforts - if at all.
Figure 10: Waxed seam area
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Figure 11: Milled, waxed joint
In this connection it must be noted that no joint wax may penetrate the joints
because otherwise the joint-sealing compound may come off. Should joint wax
penetrate the joints, the joints must be reworked with the joint cutter.
2. Wrong position of the spatula
The protrusions of the joint-sealing compound are pressed into the joint with a
spatula directly after fitting, running the spatula even over the joint.
The excessive joint-sealing compound is pressed to the left and right of the joint.
The joint-sealing compound in the joint must be separated from the material
pressed to the side.
Figure 12: Correct, flat position of the spatula
The next figures show such a joint with groove. In the course of use, collection of
dirt will result in a visually unattractive joint and complaints are certainly to be
expected.
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Figures 13+14: An excessively steep, almost vertical position inevitably results in
grooves
3. Missing cordoning off / discolourations by joint-sealing compound
Unfortunately, it often happens that the area sealed with the joint-sealing
compound is not cordoned off until the compound has been fully hardened or
premature walking on the surface may result in discolourations by the joint-sealing
compound, as shown by the following images:
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Figures 15+16: Discolourations caused by joint-sealing compound
The joint-sealing compound takes 12 hours to harden. During this time, the joints
may not be walked on. If joint-sealing compound is spilled on non-waxed areas, it
must be immediately removed – our nora® liquid wax has also proven worthwhile
for emergency cases in this respect.
For detailed recommendations in connection with the joint-sealing of nora® floor
coverings, please visit installation recommendations / sealing on our Website
www.nora.com
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